Valence and Na content dependences of superconductivity in NaxCoO2∙yH2O
Hiroya Sakurai, Naohito Tsujii, Osamu Suzuki, Hideaki Kitazawa, Giyuu Kido, Kazunori Takada, Takayoshi Sasaki, Eiji Takayama-Muromachi
DOI 10.1103/PhysRevB.74.092502 · Physical Review B
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Abstract
In order to acquire knowledge of the general superconducting phase diagram of sodium cobalt oxyhydrate, various samples with relatively large amounts of Na+ ions were synthesized by a modified soft-chemical process in which a NaOH aqueous solution was added in the final step of the procedure. From these samples, a superconducting phase diagram was determined for a section of cobalt valence of ∼+3.48, which was compared with a previously obtained one of ∼+3.40. In addition, it was proven that the superconductivity was significantly affected by the isovalent exchange of Na+ and H3O+, implying that the eg′ bands play an important role in the superconductivity. Furthermore, the high-field magnetic susceptibility measurements for one sample indicated an upper critical field much higher than 8T.
Source-reported materials — not catalogue approval
| Formula | Reported Tc (K) | Pressure (GPa) | Type |
|---|---|---|---|
| NaxCoO2∙yH2O Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula. | 5 | Pressure not reported | onset |
| Nax(H3O)zCoO2∙y'H2O Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula. | 4.7 | Pressure not reported | unknown |
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